Hypertext Help with LaTeX

\hline

The \hline command will draw a horizontal line the width of the table.
It's most commonly used to draw a line at the top, bottom, and between
the rows of the table.

Two successive \hline commands leave a space between the
lines; this space does not contain the vertical lines
specified by | characters in the col argument of the
\begin{tabular}{col} command.

To place a line at the bottom of a table, the \hline command
must follow a \\ (line break) command
after the last table entry. This final line break command should be
present only in this circumstance.